Device for the fine adjustment of a balance wheel/hairspring

ABSTRACT

In order particularly to put a watch into beat and adjust the isochronism, in addition to the poising screws ( 2   a,    2   b ) of the balance ( 1 ) and the fine adjusting screw ( 7 ) pressing on the index tail  20   a  to alter the orientation of the index ( 20 ), the device includes, on the one hand, two screws ( 19, 29 ) respectively fixed in the balance cock ( 10 ) and in the index ( 20 ) to manoeuvre clamps by means of L-shaped rocking elements ( 13, 23 ) to fix the end of the balance spring and define its useful length, and on the other hand, a screw ( 9 ) for immobilising the index ( 20 ) in a determined position, these three screws ( 9, 19, 29 ) enabling a fine adjustment to be carried out.

The present invention concerns fine regulating device for a sprungbalance consisting in a particular arrangement of the index assembly tomake adjusting the isochronism easier and more reliable in the longterm. The invention also concerns a fine adjusting method, i.e. asuccession of manipulations ranging from putting the watch into beat tothe final adjustment, the initial and final manipulations being carriedout by means of a single fine adjusting device owing to said particulararrangement.

In a known manner, an index assembly is made up of a set of partsmounted on the balance-cock, namely a balance-spring stud for securingthe end of the outer curve of the balance-spring, and an index frictionfitted onto the top balance endpiece comprising an extension beyond thebalance-cock for the pins and/or the balance-spring buckle and at theother end a tail of the index on which a screw generally acts, againstthe return force of a spring, to rotate the index through small anglesand thus modify the active length of the balance-spring.

The construction of the index assembly has given rise to a certainnumber of variants and improvements, particularly as regards the meansfor securing the external end of the balance-spring, and delimiting theactive length of said balance-spring.

All of these constructions have in common the fact that the adjusting orsecuring means are generally complicated, which can make the adjustingoperations difficult, particularly the fine adjustment of theisochronism.

It is thus an object of the invention to overcome the drawbacks of theprior art by providing a device that is much easier to handle owing to aparticular arrangement of tightening/locking devices for adjusting thesetting into beat and the rate by means of a single fine adjustingdevice. This arrangement also saves the use of a mobile stud-carrier foradjusting the setting into beat.

The invention therefore concerns a fine adjusting device for asprung-balance. The balance, which, in a conventional manner, comprisespoising screws screwed into its arms, has its axis pivoted between aplate and a balance-cock, whose top balance endpiece allows the frictionfit mounting of an index that can be oriented, for example by means of aadjusting screw pressing onto the tail of the index against the returnforce of a spring. The balance-spring, pinned up to the collet inaccordance with known means on the balance staff can be put into beat,adjusted as regards isochronism and have its outer curve fixed, owing tothe fine adjusting screw and specific tightening/locking means on thebalance cock and index whose features are explained hereinafter. Thebalance cock is provided with a first lug extended by a bent stirrupwhose feet extend as far as the outer curve of the balance spring and inwhich a first tightening device is hinged formed of an L shaped rockingelement the small arm of which is manoeuvred by a flanged screw screwedinto said lug to make the large arm pivot and to form a clamp for theend of the balance spring with the inner surface of the stirrup feet.The index comprises, on an extension opposite the index tail, a secondtightening device having the same design as the first, namely a stirrupin which an L shaped rocking element is hinged, whose flanged screwforms a clamp, by being screwed in, for fixing a chosen location of thecurve outside the balance spring in order to delimit the useful lengththereof. The balance cock includes finally a second lug into which athird screw is screwed through an oblong aperture in an annular tongueextending on one side the extension of the index, said screw locking theindex in a pre-determined position by screwing in/unscrewing the fineadjusting screw. The axis of all three tightening/locking screws isparallel to the balance staff and they are all accessible from the sameside of the device, which facilitates the adjustment operations.

This construction also has the advantage of being able to exert adefined tightening force on the outer curve of the balance spring,substantially perpendicular to the buckle, and not causing anydeformation of the latter while giving the surfaces opposite the clampsformed by a stirrup and an L-shaped rocking element the same curvatureas that of the outer curve of the balance spring.

Other features and advantages of the present invention will appear inthe following description, given by way of illustrating and non-limitingexample, with reference to the annexed drawings, in which:

FIG. 1 is a top perspective view of a sprung balance according to afirst embodiment of the invention;

FIG. 2 is a bottom perspective view of the sprung balance shown in FIG.1;

FIG. 3 is an enlarged bottom view of the tightening device along arrowIII of FIG. 2;

FIGS. 4A and 4B show in cross-section, in an open position and a closedposition the tightening device in the balance cock;

FIG. 5 shows a cross-section of the tightening device in the closedposition at the index;

FIG. 6 is a top perspective view of a sprung balance according to asecond embodiment of the invention;

FIG. 7 is a bottom perspective view of the index shown in FIG. 6; and

FIGS. 8, 9, and 10 are partial cross-sections along the lines VIII, IXand X of FIG. 6.

FIGS. 1 and 2 show perspective, respectively top and bottom views, of asprung balance according to a first embodiment of the invention, theassembly having to be secured to a plate of a mechanical watch movement(not shown). In this example, the balance 1 comprises two arms 1 a, 1 binto which poising screws 2 a, 2 b are screwed, its staff 3 beingpivoted between a plate (not shown) and a balance cock 10. In aconventional manner, FIG. 2 shows that balance 1 includes a small roller6 a, a large roller 6 b with an impulse pin 6 c, and that a collet 5allows the curve at the centre of a balance spring 4 to be fixed tostaff 3 of balance 1.

Referring more particularly to FIG. 1, it can be seen that balance cock10 carries an index 20, friction fitted onto top balance endpiece 10 aand whose tail 20 a allows its orientation to be altered owing to a fineadjusting screw 7 pressing on said tail of index 20 a against the returnforce of a swanneck shaped spring 8, through one end of which, fixed inbalance cock 10 by means of two screws 8 a, said fine regulating screw 7passes.

Balance cock 10 includes a first lug 11 provided with a first tighteningdevice forming a clamp. This device is formed by a bent stirrup 12integral with first lug 11 and whose feet 12 a, 12 b extend as far asbalance spring 4, and in which an L-shaped rocking element 13 is hinged,which can be operated by a flanged tightening screw 19 to form a clampused for immobilising the end of the outer curve 4 a of balance spring4. The detailed description and operation of this clamp assembly will bedisclosed hereinafter.

Likewise, index 20 comprises a second tightening clamp device formed,opposite index tail 20 a, by an extension 21 prolonged by a bent stirrup22 in which an L-shaped rocking element is hinged, for clamping aportion of the outer curve 4 a and thus defining the useful length ofbalance spring 4 by acting on a second flanged tightening screw 29.Extension 21 further comprises, on one of its sides, an annular tongue31 extending above a second lug 30 of balance cock 10. Tongue 31comprises an oblong aperture 32 into which there is screwed a screw 9for locking index 20 in a determined position after the orientationthereof has been adjusted by means of fine adjusting screw 7.

As can be seen in this embodiment, the three screws 9, 19 and 29 and thetwo poising screws 2 a, 2 b are all accessible from the same side, alonga direction parallel to the balance staff.

The clamps enabling the outer curve 4 a of the balance spring 4 to befixed are described with reference also to the partial bottom view ofFIG. 3 and to FIG. 4A showing in cross-section, along a line passingthrough the balance staff, the clamp formed at balance cock 10 byrocking element 13, said clamp being in the open position.

L-shaped rocking element 13 comprises a small arm 14, a large arm 15 anda hinge 13 a formed, for example, by two studs engaged in correspondingapertures in stirrup 12 of balance cock 10.

Small arm 14 comprises a notch 14 a delimited by a top lip 16 and abottom lip 18. Top lip 16 comprises an inclined plane 16 a directedtowards the interior of notch 14 a, said inclined plane 16 a cooperatingwith an inclined plane 16 b of tightening screw 19 to pivot rockingelement 13, by unscrewing said screw, and opening the clamp. Bottom lip18 is longer and extends under the flange of tightening screw 19, suchthat screwing said screw closes the clamp, as shown in FIG. 4B.

Large arm 15 comprises at its base a shoe 17, the ends of which extendon each side facing the inner surface of feet 12 a, 12 b of stirrup 12.Shoe 17 and feet 12 a, 12 b have the same curvature as the outer curve 4a of balance spring 4 such that tightening the clamp does not cause anydeformation of the strip of the balance spring 4.

The clamp formed at index 20 by rocking element 23, shown incross-section in the closed position in FIG. 5, has exactly the samefeatures as those previously described. Rocking element 23 operated byflanged tightening screw 29, comprises a small arm 24 with a notch 24 adelimited by a top lip 26 with an inclined plane 26 a cooperating withan inclined plane 26 b of the flange of screw 29, a bottom lip 28 and alarge arm 25 that ends, at its base, in a shoe 27 opposite feet 22 a, 22b of stirrup 22.

Owing to the device that has just been described, it is possible toregulate the balance spring by carrying out, in succession, theoperations set out hereinafter.

1. Putting into Beat

First of all, screw 19 is unscrewed to open the clamp secured to balancecock 10 and screw 9 is loosened to make a first rough adjustment byrocking index 20. A fine adjustment is then made by manoeuvring screw 7which acts on index tail 20 a, then screw 9 and next screw 19 aretightened.

2. Adjustment of the Isochronism

First of all, screw 29 is unscrewed to open the clamp secured to index20, then screw 9 is loosened. The angle of attachment of balance spring4 is then altered by manoeuvring fine adjusting screw 7 to optimise theisochronism, then screw 9, and next screw 19 are tightened again.

3. Rough Adjustment

The rate is adjusted by means of poising screws 2 a, 2 b, which allowthe moment of inertia of the balance to be altered.

4. Fine Adjustment

First of all, screw 29 is unscrewed to open the clamp secured to index20, then screw 19 is loosened. Acting on screw 7 can then carry out thefine adjustment. In this step, only slight variations in the isochronismcan be expected. Finally, first of all screw 9, then screw 29 aretightened again.

As can be seen, with the exception of fine adjustment screw 7, all ofthe other screws for carrying out the adjustment are accessible from thesame side.

With reference now to FIGS. 6 to 10, a second embodiment will bedescribed hereinafter, which differs from that previously describedessentially in the way in which the tightening devices are actuated. Thecommon parts, i.e. those that have not undergone any significantmodification, will bear the same references and will not be describedagain.

It can be seen first of all that index 20 has the simplified shape of anopen ring that no longer comprises an index tail and nor, therefore, theadjusting device which was formed by screw 7 and the swanneck shapedspring 8. It will be observed that such a simplification would beequally applicable to the first embodiment. Index 20 comprises anannular ring 31 provided with an oblong aperture 32 in which there isengaged a screw 9 to be screwed into a lug 30 in balance cock 10 forimmobilising index 20 in a given position as can be seen in FIG. 9.

Index 20 also comprises an extension 21 on which there is mounted atightening device that no longer includes a rocking element, but actslike a vise comprising two jaws 33, 35. An L-shaped fixed jaw 35includes a small arm 34 fixed to extension 21 by being driven in orriveted by two studs 34 a, 34 b, and a large arm 36 through which aconical head screw 39 passes, for manoeuvring a mobile jaw 33 comprisinga guide catch 33 a on small arm 34. By screwing/unscrewing screw 39 in adirection parallel to the plate, it is thus possible to immobilise orrelease the outer curve of the balance spring 4 to carry out theadjustment operations.

In order to immobilise balance spring 4, a second tightening deviceforming a vise 45, identical to the first, is mounted on a plate 47fixed to balance cock 10 by means of a screw 48 a and a stud 48 b. Aspreviously, there is thus again a fixed jaw 45, and a mobile jaw 43assembled via a conical head screw 49, enabling the sprung balance to beeasily adjusted.

The operation of this second embodiment is identical to the first, andthus will not be described any further.

Without departing from the scope of the present invention, those skilledin the art can make alterations to the embodiments that have just beendescribed, for example by giving the L-shaped rocking element adifferent shape or by changing the orientation thereof by 180°.

1.-8. (canceled)
 9. A fine adjusting device for a sprung balance, formed of a balance provided with poising screws, pivoted between a plate and a balance cock supporting an index, and a balance spring, by means of poising screws and tightening devices provided at the balance cock and the index, wherein the balance cock is provided with a first lug comprising a first device tightening the end of the balance spring, said device being formed by a clamp comprising a fixed arm in the shape of a stirrup extending said lug perpendicularly and in which there is hinged an L-shaped rocking element that can be manoeuvred by a flanged screw, wherein the index is provided with an extension comprising a second device tightening the outer curve of the balance spring, said device being identical to the first and able to be manoeuvred by a flanged screw, and wherein the balance cock is provided with a second lug comprising a third tightening device formed by a screw screwed into said lug through an oblong aperture of an annular extension of the index to lock said index in a determined position, the three screws enabling a fine adjustment to be carried out.
 10. A fine adjusting device for a sprung balance, formed of a balance provided with poising screws, pivoted between a plate and a balance cock supporting an index, and a balance spring, by means of poising screws and tightening devices provided at the balance cock and the index, wherein the index is provided with a first lug in which there is fixed a first device tightening the outer-curve of the balance spring, said device being formed by a vise comprising a fixed jaw secured to the first lug and a mobile jaw that can be manoeuvred by a conical head screw, and wherein the balance cock is provided with a second device for tightening the end of the balance spring, said device being identical to the first and fixed in a plate secured to the balance cock and able to be manoeuvred by a conical head screw and wherein the balance cock is provided with a second lug including a third tightening device formed by a screw screwed into said lug through an oblong aperture of an annular extension of the index to lock said index in a determined position, the three screws enabling a fine adjustment to be carried out.
 11. The adjusting device according to claim 9, wherein each rocking element is formed by a large arm and a small L-shaped arm including a notch delimited by a top lip and a bottom lip, in which the flange of the associated screw engages to open or close the clamp formed by the stirrup and the large arm.
 12. The adjusting device according to claim 11, wherein the top lip of the L-shaped rocking element includes a plane inclined towards the notch cooperating with a corresponding inclined plane of the flange of a tightening screw to open the clamp by being unscrewed.
 13. The adjusting device according to claim 11, wherein the bottom lip of the L-shaped rocking element is longer than the top lip and extends under the flange of a tightening screw to close the jaw by being screwed in.
 14. The adjusting device according to claim 9, wherein the large arm of an L-shaped rocking element ends in a shoe the ends of which abut against the base of the stirrup while having a curvature corresponding to that of the outer curve of the balance spring.
 15. The adjusting device according to claims 9, wherein the poising screws of the balance have a cylindrical head with a cut face.
 16. The adjusting device according to claims 9, wherein the index is further provided with an index tail able to be manoeuvred by a screw against the force of a return spring. 